Partially fluoroelastomers such as copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), and terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) have been used for a variety of applications. Cure systems such as a peroxide cure system, amine cure system, and polyol cure system can be used to cross-link the partially fluorinated elastomer gums.
Compression set resistance is the ability of the material to retain its original shape/size when deformed by a force and the force is removed. The crosslinking density is one factor influencing the compression set of partially fluorinated elastomers. Crosslinkers can be used (e.g., bisphenol AF or its complexes with benzyltriphenylphosphonium chloride), however, as the amount of crosslinker is increased, cure speed is decreased.
Mooney viscosity is another factor influencing the compression set of partially fluorinated elastomers. In polyol cure systems, typically, partially fluorinated elastomers having a higher Mooney viscosity, have a lower compression set. However, the higher the Mooney viscosity, the more difficult it can be to process the partially fluorinated elastomer gum.